A well known feature of internal combustion engines of the diesel type is their relatively high compression ratio. This is required in order to raise the temperature of the air contained in the cylinders in the final compression stage to a value high enough to accomplish ignition of liquid fuel injected into the cylinders but, unfortunately, this is most difficult to accomplish under some conditions. In particular, it is difficult to raise the temperature of the air to a sufficiently high value to accomplish fuel ignition at start-up in low ambient temperatures.
Generally speaking, it is recognized that starting characteristics can be considerably improved by supplying hot air to the inlet manifold in severe start-up conditions. It has also been known that the power of diesel engines can be increased by introducing a greater mass of combustion air into the cylinders. In addition, it is recognized that a compressor for this purpose may be driven by a turbine to provided a greater mass of combustion air.
By way of example, Melchior U.S. Pat. No. 3,849,988 discloses a turbine-compressor unit for a diesel engine. The turbine is driven by a separate combustor that receives oxygen-poor gas from the diesel engine and oxygen-rich gas from the compressor with the relative proportions being dependent upon the speed of operation. Unfortunately, there is no means for cooling the combustor and/or turbine in a manner reducing external heat losses.
For this reason, Melchior has failed to optimize the operating characteristics of the diesel engine by reason of the heat losses. Similarly, Gratzmuller U.S. Pat. No. 3,450,109 discloses the desirability of a combustor for a supercharged diesel engine but, again, the combustor is entirely separate from the compressor and turbine with no means of avoiding external heat losses. As a result, Gratzmuller has also failed to optimize the operating characteristics of the diesel engine.
In contrast, Jackson U.S. Pat. No. 2,669,090 discloses a combustion chamber for driving a turbine which employs a flame tube spaced from an enclosing housing. Air is admitted under pressure to the enclosing housing for supporting combustion and for cooling the housing and the flame tube as well as the combustion gases. However, once again the combustor is separate from the turbine, heat losses from the turbine are still present, and performance of the engine is not optimal.
For these reasons, it is an object of the present invention to provide a turbocharger-gas turbine for an internal combustion engine. It is a further object of the present invention to provide such a turbocharger-gas turbine which is operable in multiple modes, i.e., a first, or starting, mode, a second, or normal running, mode, and a third, or power boost, mode. Further, it is an object of the present invention to reduce heat losses by providing a relatively cool blanket of air around the outer skin and auxiliary burner-containing turbine assembly.
The present invention is directed to overcoming the above stated problems and accomplishing the above stated objects.